When Large sections of precast concrete pipe are to be laid to form a continuous pipe, one or more cranes are used, usually equipped with slings made of steel cable to lift and position the pipe sections. Each concrete pipe section is usually precast with a male connection at one end and a female connection at the opposite end. Typical of these precast connections are the bell-and-spigot and the tongue-and-groove, each of which has a tapered portion for insertion into a shaped recess to form a joint between the pipe sections.
Great care must be taken in maneuvering a large section of precast concrete pipe to avoid damage to the connectors at each end. The bell is usually thinner than the wall of the concrete pipe and the spigot is tapered and has a narrow leading edge. If care is not exercised in bringing the sections of concrete pipe together, it is possible for the bell or spigot to be damaged beyond repair, destroying the entire usefulness of the section of pipe. A tongue-and-groove pipe is also subject to damage in laying contiguous sections. In view of the shape of the bell-and-spigot and the tongue-and-groove, there is no convenient way to cam one pipe section against the other to bring the sections into alignment without risk of serious damage.
Concrete pipes have also been designed with cast-in-place threaded reinforcing rods which are used in combination with washers and nuts to join the pipe sections together. The end of the threaded reinforcing rod would project several inches beyond the end of the pipe and a suitable aperture would be provided in the previously laid pipe for receiving the threaded reinforcing rod in the alignment of the pipes. Care must be exercised in maneuvering this type of precast concrete pipe so as not to bend or strip the threads off the end of the threaded reinforcing rod. If the end of the reinforcing rod is damaged, time must be spent in repairing the rod, if it is capable of being repaired. If the end of the rod is destroyed beyond repair, the entire section of pipe is lost. As in the case of the bell-and-spigot and tongue-and-groove precast concrete pipe, there is no convenient way for aligning the pipe sections using the threaded reinforcing rods without risking damage to the rods.
The lifting and handling of large precast concrete pipe presents multiple problems. For example, the shear mass of the individual pipe sections can lead to serious damage if not properly controlled. Also, the fragile nature of the pipe connectors also requires care so as not to chip an edge or bend a threaded connecting rod.